Arrangement for sealing a hydrualic control device

ABSTRACT

For a hydraulic control device (12) in an automatic transmission (1), it is proposed that the intake channel (7) of a pump be surrounded by a distribution channel (9) so that during the intake of air leakage is prevented.

The invention concerns an arrangement for sealing a hydraulic controldevice which is assembled on the underside of an automatic transmission.The electromagnetic actuators and hydraulic valves are in the hydrauliccontrol device.

BACKGROUND OF THE INVENTION

By the expression automatic transmission, used in the preamble, is to beunderstood both stepped and continuously variable automatictransmissions. Electrohydraulic automatic transmissions are composed ofthe following units: a starting unit such as a hydrodynamic converter,clutch/brakes, a hydraulic control device and an electronic transmissioncontrol device. The electronic transmission control device forms, fromthe input variables, the parameters required for control of theautomatic transmission. Input variables are signals prepared by sensorsand signals made available by other electronic control devices such asthe engine control device. The electronic transmission control devicecontrols, via output signals, the electromagnetic actuators which are inthe hydraulic control device. Gearshifts are initiated, via theelectromagnetic actuators, by selecting an adequate clutch/brakecombination. The pressure distribution during the gearshift and thepressure level outside the gearshift are additionally controlled by theelectromagnetic actuators.

From the prior art, for example DE-OS 40 41 253, automatic transmissionsare known where the hydraulic control device is assembled on theunderside. The hydraulic control device consists of one intake snorkel,one valve housing, one intermediate plate with a seal and one channelplate. Here the channel plate and the transmission housing come intocontact by two surfaces. These two surfaces are designed as sealingsurfaces. As a result of the setting properties, a change of thepre-load force of the clamping bolts and leakage can occur in thisplace. Since the hydraulic control device can only be partly wetted bythe lubricant pan, leakage results in that the pump, via the intakechannel, sucks air from the interior of the transmission instead ofsucking hydraulic fluid from the lubricant pan.

SUMMARY OF THE INVENTION

The problem to be solved by the invention is thus to ensure a reliablesuction for the hydraulic control device.

According to the invention, the problem is solved by the channel platehaving at least one intake channel, one main pressure channel, andmeasuring and distribution channels wherein the intake channel issurrounded at least partly by a distribution channel. The distributionchannel holds a higher pressure level than the intake channel. Thedistribution channel is between the intake channel and the outer side ofthe channel plate. The advantage obtained by this solution, according tothe invention, is that leakage at the channel plate/transmission housingsite does not result in the suction of air. Since the intake channel issurrounded by a distribution channel with a higher pressure level, theleakage causes the intake channel to suck the hydraulic fluid from thisdistribution channel.

In another embodiment, it is proposed that the main pressure channel beat least partly surrounded by pressureless auxiliary channels situatedbetween the main pressure channel and a measuring channel. The advantageof this embodiment is that an adulteration of the pressure level withinthe measuring channel, in the case of leakage, is effectively prevented.In the case of leakage, the hydraulic fluid reaches the pressurelessauxiliary channels from the main pressure channel. The hydraulic fluidthus cannot reach the measuring channels.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment is shown in the drawings. They show:

FIG. 1 is an arrangement and a design of a hydraulic control device; and

FIG. 2 is a channel plate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows the arrangement and design of a hydraulic control device12. This hydraulic control device is a component part of the automatictransmission 1 and is within the housing 2. The hydraulic control device12 is secured to sealing surface A of the transmission housing 2 bymeans of bolts 13. The hydraulic control device 12 is composed of onesnorkel with a sieve 3, one valve housing 4, one intermediate plate witha seal 5 and the channel plate 6. The hydraulic control device 12 ispartly wetted by the lubricant pan. It is known that the level of thelubricant pan is adjusted so that the snorkel and the sieve 3 arecovered with lubricant in all driving situations. In FIG. 1 saidlubricant level is shown by reference letter B. The lubricant level Bthus does not reach the sealing surface A. One pump, not labeled in FIG.1, which is situated in the automatic transmission sucks, throughout thehydraulic control device, the lubricant from the lubricant pan by meansof the snorkel 3. The intermediate plate with seal 5 is between thevalve housing 4 and a channel plate 6. The sealing of channel plate 6relative to the transmission housing 2, sealing surface A, is absolutelymetallic. No other seal can be situated, between the channel plate 6 andthe housing 2, due to the setting properties of the bolts 13.

FIG. 2 shows a top view of the channel plate 6. The sealing surface A isshown shaded. The reference numeral 7 shows an intake channel throughwhich the pump sucks the lubricant from the lubricant pan via thesnorkel. Vacuum thus prevails in the intake channel 7. Due to thesetting properties of the bolts 13, leakage results. According to theprior art, the intake channel 7 would, in this case, suck air from theinterior of the transmission housing 2. The solution, according to theinvention, now consists in that the intake channel 7 is surrounded, inthe direction of the outer side of the channel plate, by thedistribution channel 9. The distribution channel 9 holds a higherpressure level than the intake channel 7, for example, 2 bar. In case ofleakage, the intake channel 7 thus sucks the hydraulic fluid from thedistribution channel 9. Another embodiment is also shown in FIG. 2. Thereference numeral 8 shows the main pressure channel which holds apressure level, for example, of 16 bar. The reference numeral 10 shows ameasuring channel which serves, for example, to measure the pressurelevel in the converter clutch. According to the prior art, leakage wouldcause the hydraulic fluid to migrate from the main pressure channel inthe direction of the measuring channel 10 and thus adulterate the resultof the measurement. The solution, according to the invention, nowconsists in that an auxiliary channel 11 is situated between the mainpressure channel 8 and the measuring channel 10. The auxiliary channel11 is pressureless. A leakage thus causes the hydraulic fluid to migratefrom the main pressure channel to the auxiliary channel 11 and is thusunable to reach the measuring channel 10.

The solution, according to the invention, can be used in the followingcases:

sealing points of the intake channel with vacuum which eitherpermanently, or in certain driving situations, are not in the lubricantpan;

critical pressure channels in which channels, extending side by side,have great pressure differences, for example, a main pressure channelwith 16 bar and a measuring channel with 5 bar.

Typical spheres of use would thus be the hydraulic control device ofstepped and continuously variable automatic transmissions.

    ______________________________________    Reference numerals    ______________________________________             1  automatic transmission             2  transmission housing             3  snorkel with sieve             4  valve housing             5  intermediate plate with seal             6  channel plate             7  intake channel             8  main pressure channel             9  distribution channel            10  measuring channel            11  auxiliary channel            12  hydraulic control device            13  bolts            A   sealing surface            B   lubricant level    ______________________________________

I claim:
 1. An arrangement sealing a hydraulic control device (12) whichis assembled on an underside of an automatic transmission (1) includinga housing (2) so that said hydraulic control device (12) is only partlywetted by the lubricant pan, said hydraulic control device (12)comprising one intake snorkel (3), one valve housing (4) connectedtherewith, one intermediate plate with a seal (5) and one channel plate(6), said hydraulic control device (12) is secured to said transmissionhousing (2), said channel plate (6) and said transmission housing (2)coming into contact with one another by two sealing surfaces, one pumpsucks the hydraulic fluid from said lubricant pan through said hydrauliccontrol device (12) or advances the hydraulic fluid with high pressurelevel to said valve housing (4) which is adapted to houseelectromagnetic actuators and hydraulic valves by which the clutches orbrakes of said automatic transmission are controlled, wherein saidchannel plate (6) has at least one intake channel (7), one main pressurechannel (8), and distribution and measuring channels (9, 10), saidintake channel (7) being at least partly surrounded by one distributionchannel (9), said distribution channel (9) holds a higher pressure levelthan said intake channel (7), and said distribution channel (9) isbetween said intake channel (7) and an outer side of said channel plate(6).
 2. The arrangement according to claim 1, wherein said main pressurechannel (8) is at least partly surrounded by pressureless auxiliarychannels (11), the latter being situated between said main pressurechannel (8) and a measuring channel (10).